1. Field of the Invention
This invention relates to a radiation image recording and read-out apparatus for exposing stimulable phosphor sheets to a radiation passing through an object to have a radiation image of the object stored thereon, exposing the stimulable phosphor sheets to stimulating rays which cause them to emit light in proportion to the stored radiation energy, and detecting and converting the emitted light into electric signals which are used to reproduce a visible image from the read-out image information. This invention particularly relates to such an apparatus in which stimulable phosphor sheets are circulated and reused for recording images and more particularly to such an apparatus in which the circulated and reused stimulable phosphor sheets can be subjected to slit image recording.
2. Description of the Prior Art
As disclosed for example in Japanese Unexamined Patent Publication No. 56(1981)-11395 and U.S. Pat. Nos. 4,258,264, 4,315,318, 4,387,428 and 4,276,473, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a sheet comprising the stimulable phosphor is first exposed to a radiation passing through an object to have a radiation image stored thereon, and is then scanned with stimulating rays which cause it to emit light in proportion to the radiation energy stored. The light emitted from the stimulable phosphor sheet when the sheet is exposed to the stimulating rays is photoelectrically detected and converted to an electric image signal, which is processed as desired to reproduce a visible image having an improved quality, particularly a high diagnostic efficiency and accuracy. The finally obtained visible image may be reproduced in the form of a hard copy or may be displayed on a display device such as a CRT (cathode ray tube).
Further, with regard to a mobile X-ray diagnostic station such as a traveling X-ray diagnostic station in the form of a vehicle like a bus which is provided with a radiation image recording and read-out apparatus for use in the aforesaid radiation image recording and reproducing system and moves from place to place to record radiation images for mass medical examinations, it is disadvantageous to load such a mobile X-ray diagnostic station with a large number of stimulable phosphor sheets, and the number of the stimulable phosphor sheets which can be loaded on the mobile X-ray diagnostic station is limited. Therefore, it is desired to load the mobile X-ray diagnostic station with stimulable phosphor sheets, transfer the electric image signals read out from the stimulable phosphor sheets to a recording medium having a large storage capacity, such as a magnetic tape, and circulate and reuse the stimulable phosphor sheets for further image recording and read-out operations, thereby to obtain the radiation image signals of many objects. Further, when image recording is conducted continuously by circulating and reusing the stimulable phosphor sheets, it becomes possible to increase the image recording speed in mass medical examinations. This is very advantageous in practical use.
In order to reuse stimulable phosphor sheets as described above, the radiation energy remaining on the stimulable phosphor sheet after it is scanned with stimulating rays to read out the radiation image stored thereon should be eliminated or erased by exposure to light or heat as described, for example, in U.S. application Ser. No. 168.806 filed July 11, 1980, now abandoned and U.S. Pat. No. 4,470,619. This stimulable phosphor sheet can then be used again for radiation image recording.
On the other hand, it has been proposed to carry out slit image recording in the aforesaid radiation image recording and read-out system employing stimulable phosphor sheets. For example, U.S. Pat. No. 4,356,398 discloses a method for realizing an improvement in image contrast by using slits to eliminate scattered rays.
It would also be very convenient if slit image recording capability could be provided in an integrated apparatus in which at least one stimulable phosphor sheet is reused by repeatedly circulating it through an image recording section for recording a radiation transmission image of an object on the stimulable phosphor sheet by exposing it to a radiation passing through the object, an image read-out section for reading-out the radiation image stored on the stimulable phosphor sheet in the image recording section, and an erasing section for releasing the radiation energy remaining on the stimulable phosphor sheet after read-out so as to prepare it for recording of the next image thereon.